Banjo-Kazooie

I would like to know the answer to Stop N Swop (if there is an answer), the mystery eggs and the ice key. What do they mean and do in Banjo-Kazooie? I know they do something in the sequel Banjo-Tooie but what do they do in Banjo-Kazooie?

Games Guru: Ah, the mysterious Stop ‘N’ Swop. The feature was never really finished when Rare added it to the game. So while they said at the end of the game that you could link to the sequel, you really can’t. Plus, the items can only be retrieved by using codes. You were supposed to be able to bring the eggs to a hen to hatch. And the ice key was supposed to open an ice vault with a special item inside. You would have been able to swap both game cartridges to use these items in the second game. But this was never implemented, perhaps because of limitations in the Nintendo 64 system.